通过下面两幅图进行分析：

                                图1 数据输入FPGA模型                                  

                                      图2input delay max/min 公式

1.对input delay max的理解：

按图1，可以得出下面公式：

data arrival time = launch edge + Tclk1(max)+Tco(max)+(Tdata_PCB(max)+Tcl)

                              +Tdatain         (式1-1)                                           

data required time = latch edge + Tclk2ext(min) + Tclk2int – Tsu     (式1-2)     

 slack = data required time - data arrival time

         = latch edge + Tclk2ext(min) + Tclk2int – Tsu –[launch edge + Tclk1(max)+

           Tco(max)+(Tdata_PCB(max)+Tcl) +Tdatain]

        =( latch edge–launch edge) +( Tclk2int – Tsu–Tdatain) –

           (Tclk1(max)+ Tco(max)+(Tdata_PCB(max)+Tcl) –Tclk2ext(min))    (式1-3)

按照图2的公式：

data arrival time = launch edge + input delay max + Tdatain                  (式1-4)

data required time = latch edge + Tclk2int – Tsu                                    (式1-5)

slack = data required time - data arrival time

             = latch edge + Tclk2int – Tsu

                –[launch edge + input delay max + Tdatain]

               = ( latch edge–launch edge) + (Tclk2int – Tsu–Tdatain ) –

                    input delay max                                                      (式1-6)

比较（式1-3）和（式1-6）可以得出(式1-7)：

input delay max = Tclk1(max)+ Tco(max)+(Tdata_PCB(max)+Tcl) –Tclk2ext(min)

                          = (Tdata_PCB(max)+Tcl) –(Tclk2ext(min) –Tclk1(max))+ Tco(max)      

                                                                                                                    (式1-7)

(式1-7)就是图2中给出的input delay max公式。

2.对input delay min的理解：

按图1，可以得出下面公式：

data arrival time = launch edge + Tclk1(min)+Tco(min)+(Tdata_PCB(min)+Tcl)

                              +Tdatain              (式2-1)        

data required time = latch edge + Tclk2ext(max) + Tclk2int +Th           (式2-2)

       slack = data arrival time– data required time

                = [launch edge + Tclk1(min)+Tco(min)+(Tdata_PCB(min)+Tcl) +Tdatain]

                    –[latch edge + Tclk2ext(max) + Tclk2int +Th]

               =( launch edge–latch edge)+( Tdatain–Tclk2int–Th) +

                 Tclk1(min)+Tco(min)+(Tdata_PCB(min)+Tcl) –Tclk2ext(max)        (式2-3)

按照图2的公式：

data arrival time = launch edge+ input delay min + Tdatain                       (式2-4)

data required time = latch edge + Tclk2int +Th                                          (式2-5)

                     slack = data arrival time – data required time

                              =[launch edge+ input delay min + Tdatain]–

                                [ latch edge + Tclk2int +Th]

                              =( launch edge –latch edge)+( Tdatain–Tclk2int–Th)+

                                 input delay min                                                            (式2-6)

比较（式2-3）和（式2-6）可以得出(式2-7)：

input delay min = Tclk1(min)+Tco(min)+(Tdata_PCB(min)+Tcl) –Tclk2ext(max)

                          =(Tdata_PCB(min)+Tcl) –(Tclk2ext(max) –Tclk1(min))

                              + Tco(min)                                      (式2-7)

 (式2-7)就是图2中给出的input delay min公式。